Room register locations
teddymack
| Posted in General Questions on
We live in Casper, Wyoming and we are buying a house that we want to totally change the heating system. We will go with a total forced air heating and cooling package and there are no ducts at present. The house is only 1500 sq. ft. and is a single level with a crawl space. The first heating contractor I have talked with recommends ducting thru the attic to ceiling registers and then a floor area cold air return in each room. Will this provide the comfort we want vs a floor discharge system?
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Replies
Depends on how much demolition you want to do.
Ideally your HVAC contractor should be competent in Manual J, S, T, and D calculations. Do they have experience installing rigid duct or is it flex-duct? If they're not familiar with these things then I would hold out and look elsewhere.
Today HVAC systems in a VENTED attic are frowned upon as it'll cost you $ in the form of upsized equipment and loss of efficiency.
http://www.energyvanguard.com/blog-building-science-HERS-BPI/bid/37620/The-Ductopus-or-the-Centipede-Which-HVAC-Duct-System-Is-Better
Chris,
You should never run ducts outside of your home's thermal envelope.
If you want to run ducts in your crawl space, you must first make sure that the crawl space has no vents and that the crawl space walls are insulated. Here is a link to an article that describes the work: Building an Unvented Crawl Space.
If you want to run ducts in your attic, you must first make sure that the attic is an unvented, conditioned attic (not the usual type of attic, which is called a vented, unconditioned attic). Here is a link to an article that describes the work: Creating a Conditioned Attic.
Assuming that the ducts are located inside your home's thermal envelope, either approach can work. Other factors -- good duct design, careful duct sealing, and proper selection of registers or diffusers -- matter more than whether the registers and diffusers are located in the floor or in the ceiling.
HVAC contractors seem more comfortable cutting & patching through ceiling gypsum than dealing with finished floors. I've fought this battle more than once. But it's usually much cheaper & easier to air-seal & insulate the crawl space than to do a credible job of it in the attic.
Depending on the actual Manual-J numbers and layout, it may be possible to heat & cool the place with one or two mini-ducted mini-splits with the cassettes mounted in the crawlspace. I lost that battle on a recent project, where the available contractors flat out refused. But rather than installing ducts in the attic I steered them to a wall-coil type multi-split solution that was sub-optimally oversized- far less than perfect, but still better than ducts in the attic. (Had it been my house I would have done it myself.)
Given the heavy use of coal for electricity in WY a mini-split heat pump solution would have heavier carbon footprint than condensing gas in Casper WY, unless you had an option to buy wind power or something. (Been meaning to write up a blog bit on how to figure that stuff out...)
Years back I used to work with radio and television production trucks where the biggest challenge was usually cooling because of the electronics equipment. Generally these vehicles had combo rooftop air-conditioning / heat units. They were truly lousy the few times of the year that we used the heat setting, your feet were always cold. I worry that there may be parallels for you.
I suppose maybe in the southern states where it's typically a cooling dominated environment it's OK to get heat from the ceiling the rare chilly day. I would wonder though about Casper, Wyoming. I think it's cold there?
Does the cold return at the floor make a difference? Look forward to hearing if that is so.